The Aquagraph is a superb diving watch made for practical use—it just so happens to look great as an added bonus. It is remarkable for being the first watch ever made with a chronograph function that you can use underwater. Most chronos let water in when their buttons are operated, but the Aquagraph was built with special rubber pushers that remain sealed at all times—to our knowledge, this makes it the only mechanical watch that can do this. You still can't unscrew the crown to set the time while below the waves, but there is a little coloured gasket that becomes visible if you attempt to do so, warning you that water resistance has been compromised. The caseback is engraved with an illustration of an old-fashioned diver's helmet.